Evidence for Transport of Photosynthetic Products in the Phloem Flashcards
(21 cards)
What is the name for the experiment that shows translocation occurs in the phloem?
Ringing/ girdling
What does ringing involve?
Removing a complete ring of phloem around a part of the plant preventing transport
What was this experiment tested on?
A part of a tree trunk
What happened after a few months of ringing the tree trunk?
A slight swelling develops above the ring
What was this swelling linked to?
The build-up of photosynthetic products which couldn’t get past the ring
Which radioactive isotopes can be used as a tracer?
14 C
What is the first step for a method including this isotope?
Obtain two plants of the same species at similar stages of growth
What is the next step after obtaining the plants?
The stem of plant A is ringed while plant B is left intact
What is the next step after ringing plant A?
A leaf below the girdle in plant A and at a similar position on plant B is supplied with 14 C
What is the next step after supplying the leaves with 14 C?
The plants are left for a few hours in sunlight
What is the next step after leaving the plants in sunlight?
The transport of radioactive products can be detected using autoradiography
What does autoradiography involve?
Placing each plant between X-ray film which is exposed by the radioactive compounds
What does autoradiography show?
Shows their location
What does plant B show?
Transport of photosynthetic products throughout the plant particularly to sinks
What does plant A show?
Photosynthetic products cannot move past the ring and collect there
Why do some products appear above the ring?
Transport in the xylem through lateral transport
What is the evidence supporting mass flow?
Cutting the stem results in phloem sap being released indicating hydrostatic pressure, use of respiratory inhibitors reduces rate of translocation
What is the evidence against mass flow?
Structure of sieve elements is not required for mass flow, substances have been observed moving in opposite directions in the same tube
What does exudate mean?
Something has been pushed out
What do aphids do?
Insert their proboscis into the phloem
What do aphids prove?
It confirms there are carbohydrates and amino acids in the phloem
